Fuel injection pump

ABSTRACT

The invention relates to a fuel injection pump including an aperture pad mounted for sliding motion within the pump casing and interposed between a plunger piston and a tappet. Each hole of the pad is provided with an individual valve opening automatically during the upward motion of the pad through the force of inertia due to the acceleration of the pad and by the air compression within a space defined above the pad, and closing automatically during the downward motion of the pad for providing a vacuum through suction or drawing into this space.

United States Patent Bastenhof 5] Nov. 18, 1975 FUEL INJECTION PUMP [75]Inventor: Dirk 'Bastenhof, Eaubonne, France 'T E'mm" 1er ManuelAntonakas Asszslant Evammer-James W. Cranson, Jr. 1 Asslgneei 506MBDEtlldeS d6 Machines Attorney, Agent, or Firnzl(enyon & Kenyon ReillyThermiques, Saint Denis, France Carr & Chapin [22] Filed: May 21, 1974211 Appl. No.: 471,905 [571 ABSTRACT The invention relates to a fuelinjection pump includ- [30] Foreign Application Prinrity Data mg anaperture pad mounted for slldmg mot1on wlthm J 76 1973 Franc 73 73x79the pump casing and interposed between a plunger um L M piston and atappet. Each hole of the pad is provided with an individual valveopening automatically during [52] US. Cl. 123/139 AC, 123/139 AC theupward motion of the pad through the force of [51] Int. Cl. F02m 39/00[58] Field of Searchl23/ l 39 AC 139 AA 139 AR ertla due to theacceleration of the pad and by the air 123/139 139 compression within aspace defined above the pad,

and closing automatically during the downward mo- 1561 :12: :35 11211:;5111;112:3125: 3,614,944 10/1971 Ulbing 123/139 AC 4 Claims 3 DrawingFigures US. Patent Nov. 18, 1975 Sheet 1 of2 US. Patent Nov. 18, 1975Sheet20f2 3,919,990

HIE-'3.

ll 1 4 i/ 1 23 .111 25 M i111 FUEL INJECTION PUMP The present inventionrelates generally to fuel injection pumps and more particularly to animproved fuel injection pump for an internal combustion engine,comprising a constant-stroke, reciprocating plunger piston driven oroperated by a tappet, lifter or like pusher member. a

The fuel injection pumps associated with the cylinders, respectively, ofan internal combustion engine and belonging to the aforesaid kind havebeen known for a long time. In use such pumps however exhibit a numberof inconveniences such as the danger of the control toothed rackbecoming blocked or jammed through seizing or sticking thereof, whichtoothed rack. as known, provides for the control or adjustment of thefuel flow rate delivered.

More specifically the pumps in which the present invention is concernedcomprise a piston driven by a tappet and a bolster, pad or like basemember slidably mounted within the body or casing of the pump andinterposed between the piston and the tappet. Such an arrangementdefines within the body or casing of the pump two spaces or chambers,namely a first space provided above the base member or pad towards thepiston and a second space provided below the base member or pad towardsthe tappet. As the diameter of the tappet is larger than that of thebase member or pad which also forms a cup-like seat for a piston-biasingreturn or drawback spring, air is compressed within both aforementionedspaces when the tappet actuates the pad hence the piston. It resultstherefrom-that this compressed air tends to flow into the slots or slitsabout the toothed rack carrying along some fuel which thereby results inthe risk of the toothed rack becoming seized and accordingly ofimpairing or adversely affecting the correct working of the pump. It istherefore desirable to avoid any air overpressure within the spacesdefined within the casing or body of the pump on either side of the padso as to prevent any danger of the toothed rack becoming blocked orjammed.

In order to obviate such an inconvenience there has already beenproposed a simple solution consisting in providing one or severalthoroughfare holes within the pad or base member so as to establish aconstant communication between both aforesaid spaces. This would ofcourse relieve the pressure built up within the space above the pistontowards the pad, the compressed air having always the possibility toescape into the chamber located towards the tappet underneath the padbut the problem is not completely solved thereby as there will still besome air pressure present within said spaces, which would be harmful tothe proper operation of the toothed rack. i

The present invention obviates the aforesaid drawbacks by providing animproved fuel injection pump definitely preventing the sticking orseizing of the toothed rack caused by air overpressure within the pumpcasing.

More specifically the invention has for its purpose to provide a fuelinjection pump for an internal combustion engine, including aconstant-strokereciprocating piston driven or actuated by a tappet aswell as a pad, bolster or like base member interposed between the pistonand the tappet, which pad is mounted for sliding motion within the pumpcasing or body, forms a cupshaped seat for a piston-biasing returnspring and comprises at least one thoroughfare hole providingcommunication between a first space formed above the pad towards thepiston and a second space formed below the pad towards the tappet, saiddevice being characterized in that each aforesaid hole is provided witha valve opening automatically during the upward motion of the padthrough the inertia force due to the acceleration of the pad and throughair compression within said first space and closing automatically duringthe downward motion of the pad for producing a vacuum or likeunderpressure through suction or drawing in within the first space.

It is thus understandable that when the pad within the pump casing ismoving downwards under the action of the return spring, the aircontained or trapped within the space above the pad is drawn in orsucked through and past the toothed rack thereby avoiding any seizingthereof.

According to a further characterizing feature of the invention eachaforesaid valve comprises a resiliently flexible or deformable platesecured to said pad on the side of said second space formed within thepump casing between the pad and the tappet.

According to still a further characterizing feature of the invention,each aforesaid valve consists of a small disk or like plate membermounted in floating relationship within a recess or housing formed in aring-shaped element rigidly secured to said pad.

In this other form of embodiment of the valve according to the inventionit should be noted that the aforesaid recess is suitably machined toalso provide for the escape of the compressed air during the upwardmotion of the pad.

The invention will be better understood and further objects,characterizing features, detailsand advantages thereof will appear moreclearly as the following explanatory description proceeds with referenceto the accompanying diagrammatic drawings given by way of non-limitingexamples only illustrating several pres ently preferred forms ofembodiment of the invention and wherein:

FIG. 1 is a fragmentary view in longitudinal crosssection with partsbroken away, of a fuel injection pump provided with a valve according toa first form of embodiment of the invention;

FIG. 2 is a sectional view of the pad provided with a valve according toa second form of embodiment of the invention; and

FIGS is a view in cross-section taken upon the line III-III in FIG. 2. 7

Referring to FIG. 1, the known component elements constituting the fuelinjection pump accordingto the invention will be described at first.

A fuel injection pump of the kind in question essentially comprises apump barrel or casing l enclosing a constant-stroke, reciprocatingpiston 3 and a tappet 2. A pad or like base member 4 is interposedbetween the tappet 2 and the piston 3 and is mounted for sliding motionwithin the pump casing 1. As clearly shown in FIG. 1, the pad 4 forms acup-shaped seat for a return spring 5 biasing the piston 3 and comprisesa plurality of thoroughfare holes 6 providing a constant communicationbetween a first space or chamber 7 defined above the pad 4 towards thepiston 3 and a second space or chamber 8 defined below the pad 4 towardsthe tappet 2. At 9 has been shown a cam rigidly connected to a shaft 10and operating the tappet 2 by acting upon a follower or like roller 11secured to said tappet 2.

At 12 is shown a toothed rack operated by suitable means for turning theplunger piston 3 while allowing same to move upwards and downwardsinside of the pump barrel or casing l. The plunger piston 3 is as knownper se provided at its upper end portion with a helical ramp-likeformation l3 providing for the induction of fuel in accordance with therotary position of the plunger piston 3 controlled by the toothed rack12.

At 14 has been shown a breather or like snifting valve through which thespace 8 is communicating with or vented to the outer atmosphere, whichbreather or snifting valve comprises a number of baffles 15 to cause asknown per se the separation of fuel from air. Within the pump casing orbarrel 1 is also provided a duct 16 for collecting or recovering thefuel leaks. It should be noted that a snifting valve or breather such as14 may be dispensed with and when it is omitted, the entrapped air isdischarged or drained off through the duct 16.

All the elements set forth hereinabove do not call for any particularcomments since they are part of the known state of the art.

According to the present invention each thoroughfare hole 6 in the pad 4is provided with a valve 17 mounted on the side of the space or chamber8.

More specifically according to the form of embodiment shown in FIG. 1,each valve 17 merely assumes the shape of a resiliently flexible plate18 secured at 19 onto the pad 4. The fastening may be effected by anysuitable means such as rivets, screws, welding or the like. Thereby isachieved a particularly simple valving arrangement.

Referring now to FIGS. 2 and 3, there is shown a second form ofembodiment of the valve 17 according to the invention. Such a valveconsists of a disk or like small plate member 21 made from a suitablematerial so as to be able to close the thoroughfare holes 6 of the pad 4and fitted or accommodated in loosely floating relationship within arecess or like housing 22 machined within a ring-shaped holder or likeannular support member affixed to the pad 4 by any suitable means suchas screws, rivets or welding. As is better apparent from FIG. 3, therecesses 22 for the small plates or disks 21 communicate with recessedchannel portions or grooves 23 formed in the annular support orring-shaped holder 20 and enabling the air to be discharged into thespace 8 when the pad 4 is moving upwards within the pump casing.

The operation and the purpose of the valves 17 will now be brieflyexplained when the pump is in operation.

When the tappet 2 is moving upwards under the action of the cam 9 actingupon the follower or roller 11 of the tappet, it strikes or engages thepad 4 to raise the plunger piston 3 thereby causing air to be compressedwithin the space 7 and accordingly the automatic opening of the valves17. In other words, in the case of FIG. 1, the flexible plates 18 aredisengaged or move away from the thoroughfare holes 6 and in the case ofthe form of embodiment of FIG. 2, the disks 21 are resting on the bottomof the recesses 22. The air overpressure within the space 7 is therebyavoided advantageously. It should also be pointed out that the openingof the valve is facilitated to a large extent by the force of inertiadue to the acceleration of the pad 4.

Then once the pad 4 has initiated or started its downward motion thevalves 17 close automatically. i.e. as soon as the compressed air hasbeen expelled from the space 7. The valves 17 being thus closed and thepad effecting its downward motion by sliding within the pump casing I,there is provided a vacuum within the chamber 7, ie there is produced asuction past the toothed rack 12 thereby advantageously preventing sameto become seized by the fuel leaks. The compressed air within the space8 is then discharged or released through the breather or snifting valvel4 and/or through the fuel-leak recovering duct 16.

To summarize the foregoing, it may be said that when the pad 4 is movingupwards the air is not compressed or compressed very little within thespace 7 and when the pad 4 is moving downwards there is produced avacuum within the space or chamber 7 through suction or drawing intosaid chamber.

Thus, the problem set by the air overpressure inside a fuel injectionpump of the type in question and essentially due to the relatively largediameter of the tappet 2 with respect to that of the plunger piston 3 issolved advantageously according to the present invention owing to valvesprovided on the holes, respectively, of the pad and assuming the shapeeither of flexible plates such as 18 or of disks or like elements suchas 21 fitted in loosely floating relationship within an annular supportmember or holder 20 rigidly connected to the pad 4.

It should be understood that the invention is not at all limited to thetwo forms of embodiment of the valve described and shown which have beengiven by way of examples only. The invention therefore comprises all thetechnical equivalents of the means described as well as theircombinations if same are carried out according to the gist of theinvention and used within the scope of the appended claims.

What is claimed is:

l. A fuel injection pump for an internal combustion engine, including aconstant-stroke, reciprocating plunger piston driven according to astraight translatory motion by a tappet and rotated for adjustment by agear consisting of an operating control toothed rack and a driven pinioncoaxial with said plunger piston, and a pad interposed between saidplunger piston and said tappet, which pad is slidably mounted within thepump. casing while-forming a cup-like seat, a return spring supported bysaid pad and biasing said plunger piston, said pad being formed with atleast one thoroughfare hole providing communication between on the onehand a first mainly air space adjacent to said gear and defined abovesaid pad towards said plunger piston and on the other hand a secondspace defined underneath said pad towards said tappet, wherein eachthoroughfare hole is provided with an individual valve openingautomatically during the upward motion of said pad through the force ofinertia due to the acceleration of said pad and by the air compressionwithin said first space-and closing automatically during the downwardmotion of said pad for providing a vacuum through suction or drawinginto said first space.

2. A fuel injection pump according to claim 1, wherein each aforesaidvalve comprises a resiliently flexible plate covering its associatedaforesaid hole and secured on one side of said hole to said pad, on theside of said second space.

3. A fuel injection pump according to claim 1, wherein each aforesaidvalve consists of a small disk or like plate member loosely fitted infloating relationship within a recess provided in a ring-shaped elementrigidly connected in coaxial relationship to said pad, on second spaceand said recesses for allowing the comthe side of said second space.

4. A fuel injection pump according to claim 3, wherein said ring-shapedelement comprises grooves or like channels providing communicationbetween said 5 pressed air to be discharged or drained off during theupward motion of said pad.

1. A fuel injection pump for an internal combustion engine, including aconstant-stroke, reciprocating plunger piston driven according to astraight translatory motion by a tappet and rotated for adjustment by agear consisting of an operating control toothed rack and a driven pinioncoaxial with said plunger piston, and a pad interposed between saidplunger piston and said tappet, which pad is slidably mounted within thepump casing while forming a cup-like seat, a return spring supported bysaid pad and biasing said plunger piston, said pad being formed with atleast one thoroughfare hole providing communication between on the onehand a first mainly air space adjacent to said gear and defined abovesaid pad towards said plunger piston and on the other hand a secondspace defined underneath said pad towards said tappet, wherein eachthoroughfare hole is provided with an individual valve openingautomatically during the upward motion of said pad through the force ofinertia due to the acceleration of said pad and by the air compressionwithin said first space and closing automatically during the downwardmotion of said pad for providing a vacuum through suction or drawinginto said first space.
 2. A fuel injection pump according to claim 1,wherein each aforesaid valve comprises a resiliently flexible platecovering its associated aforesaid hole and secured on one side of saidhole to said pad, on the side of said second space.
 3. A fuel injectionpump according to claim 1, wherein each aforesaid valve consists of asmall disk or like plate member loosely fitted in floating relationshipwithin a recess provided in a ring-shaped element rigidly connected incoaxial relationship to said pad, on the side of said second space.
 4. Afuel injection pump according to claim 3, wherein said ring-shapedelement comprises grooves or like channels providing communicationbetween said second space and said recesses for allowing the compressedair to be discharged or drained off during the upward motion of saidpad.